Interfacing GR47 GSM module to PIC microcontroller using RS232

[barkerben]

Hi,

I have a GR47 that I want to interface to a PIC microcontroller using RS232. By default the GR47 uses hardware flow control, but for simplicity I am tempted to use software flow control only and rely on the fact my messages will be short to avoid and my interrupt response time quick to avoid buffer overrun problems.

My question is this:

hardware flow control is the default on the module. If I simply short RTS/CTS, will this be enough to let me talk to the module? There are also the DTR etc lines - I think they will not be relevant though?

Second question - I can check this myself, so shouldn't really ask here, but while I can control this module using AT commands, does GSM modules generally issue AT strings on events (SMS arrival etc?) or do they need to be continually polled...

Cheers,

Ben

 

[laktronics]

gr47 gsm pdf

Hi,
You should short RTS to CTS and DTR to DSR, since a module using hardware flow control is likely to use both controls, even though it is not always necessary.

For the second part when you find the answer, please post it here, I feel it will not give an indication and you need to poll.

Regards,
Laktronics

 

[edsonmoky]

Re: GR47 GSM module

If you go to Data communication mode and need to come back to data control mode you need to control DTR pin.
I´m not sure but GR47 doesn´t have AT+++ control, only DTR control.
Edson

 

[barkerben]

Re: GR47 GSM module

Hi - I was looking through this:

**broken link removed**

And there was no immediate indication that the DTR/DSR lines needed to be controlled, but I am still not sure how the modes differ and how they can be switched - I will need to check this...


Cheers,

Ben

Added after 50 minutes:

Ah - I found the AT command reference here:

**broken link removed**

Which again makes no reference to the need to control any pins to select mode - perhaps the pin status is merely indicative?

Added after 59 minutes:

Ah...pages 129/130 of the above document would appear to show that the DTR/DSR lines can be ignored after all...

 

[barkerben]

Re: GR47 GSM module

Looking here:

**broken link removed**

Would seem to suggest that control over the DTS line is only needed when sending data over GPRS. If I have got this right, it states that to use At commands you must be in command mode. In this mode, DTR must be low.

If you use the AT commands to set up a GPRS connection, then you must raise DTR and any incoming data gets sent across the established connection. Dropping nDTr and issuing the neccesary At commands puts you back in command mode.

So I can send SMS without control of DTR (just tying it low), but I cant set up a GPRS session without controlling it...

 

[skara1214]

Hi I have this module either and I want to send a sms to make a start but I have some problems first of all there are 3 uart on this module uart1 uart2 and uart3 which one should I use to make connection?I just use rx and tx to send a sms (rtd esc is important) And also this module work with 5 volts or 3.3 volt?